Typically, operating characteristics of a mechanical power source (e.g., an engine) do not match those of a load driven by the power source (e.g., wheels of an automobile). For example, a diesel engine might run most efficiently at 2400 rpm, but a delivery truck running onusing that engine as a power source must operate at speeds between 0 and 60 mph and under different conditions like climbing a hill or accelerating. Mismatch between the power source output speed and the load output speed leads to wastage of energy and a reduction in the overall efficiency. The transmission system is the key component that enables source and load characteristics (e.g., output speeds) to be matched efficiently. Conventional manual and automatic transmissions are a compromise by providing selectable fixed ratios of torque and speed between the source and the load for matching. Automatic transmissions also include a torque converter which connects the power source to various gears, where the best combination of the gears is selected using an external control system. The torque converter smoothes out the changes between different gear combinations and allows the transmission gears to remain engaged when the transmission output is stationary. Manual transmissions include an operator-controlled clutch which must be disengaged by the operator when different gear combinations are selected by the operator. Conventional manual and automatic transmissions use a finite number of gear ratios which are not optimal for all conditions such as varying terrain and output speeds.
The first documented continuously variable transmission was described by Leonardo daVinci in 1490 A.D. As is the case for most modern continuously variable transmission systems, daVinci's continuously variable transmission system used friction between two or more smooth surfaces to achieve an approximately continuously variable output function. Modern day conventional continuously variable transmission systems typically use a belt running between two logic-controlled adjustable sheaves. The belt system is connected to the power source using a torque converter or some form of manual or automatic clutch, depending on the field of application for the transmission. Conventional continuously variable transmission system designs are restricted in the range of gear ratios they can practically provide and usually require additional gear sets following the continuously variable transmission system, in addition to the continuously variable transmission system component itself. Additionally, conventional continuously variable transmission systems and automatic transmissions are single-input-single-output devices.